我想买五千克苹果。

Wǒ xiǎng mǎi wǔ qiānkè píngguǒ.

I want to buy five kilograms of apples.

行李不能超过二十千克，不然要多付钱。

Xíngli bùnéng chāoguò èrshí qiānkè, bùrán yào duō fù qián.

Your luggage cannot exceed twenty kilograms, otherwise you have to pay extra.

这个包只有三千克，你可以自己拿。

Zhège bāo zhǐyǒu sān qiānkè, nǐ kěyǐ zìjǐ ná.

This bag is only three kilograms; you can carry it yourself.